The exact purpose of multipool is what you are stating. Multipool wouldn't exist if it wasn't because you could do exactly what you are saying. In short, yes, it should be more profitable theoretically. Go to the site, there's a profitability indicator right at the homepage.
I went to multipool.us...It says it's currently mining Dogecoins for scrypt and the profitability is 76.46...but that is that 76.46 within a day or what? i may need a lot more than that to trade for 1 btc.
Also, after mining the profitable coin, do you immediately go to cryptsy/bter to trade for ltc/btc? or is it automated ? or can be